More on sub-mains

[JohnW2]

Following recent discussions, I have continued my exploration of my electrical installation, which has resulted in a further question. The short-form of the question is as follows; depending on replies, I can provide further background/detail if required.....

Is it acceptable to have a single switch-fuse protecting two sub-mains (wired separately from the switch-fuse) given (a) that the fuse would be satisfactory for either of the sub-mains alone and (b) that the rating of the fuse is satisfactory in relation to the total design current of all circuits involved? On the face of it, I can see no real problem with this (even in the vanishingly improbable scenario of simultaneous shorts at the end of both sub-mains), and can so far find nothing in the regs which appear to prohibit it - although, as always, I may be missing something! The context is such that lack of discrimination/selectivity between the two sub-mains circuits would not really be an 'inconvenence'.

Kind Regards, John

 

[jeepmadmike]

you would be installing larger than necessary, discrimiation and isolation are the issues

prefectly ok but not good engineering

 

[JohnW2]

you would be installing larger than necessary, discrimiation and isolation are the issues
prefectly ok but not good engineering

Thanks. This is not a proposed installation, but an existing situation which I have inherited. As I said, lack of discrimination (and, similarly, lack of ability to isolate the sub-mains separately) is really not much of a concern. My inclination is therefore to allow it to remain as it is.

Kind Regards, John.